During operation of a wind turbine, dirt and other materials may accumulate on the surface of the blades, especially on their leading edge: for example, flying insects may impact against the leading edge of the blade due to the rotation and remain attached to it, or ice can form due to the weather conditions around the blades.
The build-up of dirt or ice on the leading edge of the blade may cause a change in the profile, and therefore in the aerodynamic forces acting on the blade, such as to significantly reduce the power generated by the wind turbine, especially with strong winds; it may therefore be desirable to perform maintenance operations on the outer surface of the blade such as cleaning, wiping away insects or other dirt, removing ice, or servicing the surface of the blade in some other way.
Sometimes wind turbine blades may be cleaned by projecting water under pressure from the ground, or by hoisting cleaning staff up to the blade to perform the necessary operations; however, such solutions are far from being satisfactory.
From US2010/0003138 an apparatus is known for cleaning a leading edge of a rotor blade of a wind turbine. In this apparatus a cleaning device that may be displaced along the blade is maintained attached to the blade by magnets arranged inside the blade shell: the solution is relatively complex, and may have associated safety issues.
The aim of the present invention is thus providing a blade and a servicing unit for a blade that allow at least certain maintenance operations to be carried out on the blade surface in a safe and reliable way.